Test leaks are employed for checking and/or calibration of leak detectors which operate with a test gas. These are equipped with a capillary tube as the element which determines the leakage rate. Mostly helium is used as the test gas.
Until today, the capillary tubes for test leaks are drawn from a glass tube. Attaining a specific leakage rate requires a high degree of skill and sensitivity. Each manually produced capillary tube must be measured up on a leak detector. Thereafter, it is either discarded or redrawn and measured again. For this type of production the reject rate of the capillary tubes is therefore high. Moreover, the drawn capillary tubes (having a diameter of several tenths of a millimeter) are exceptionally prone to breakage. Even capillary tubes which are contained in a housing may be destroyed by mechanical influences.